1. Field of the Invention
The present invention relates to an apparatus for and method of detecting a cell abnormality by calculating through an arithmetic operation the state of depletion of a battery pack mounted on an electric car or the like.
2. Description of the Related Art
The methods adopted in the related art to calculate the state of depletion of a battery pack mounted an electric car or the like include a method through which the total voltage at the battery pack is detected and an average deterioration factor for all the cells is calculated based upon the detected total voltage and the charging/discharging currents flowing at the battery pack (see Japanese Laid-Open Patent Publication No. 2000-261901). In this method, the average deterioration factor of all the cells is calculated through a regression analysis executed by sampling the total voltage and the charging/discharging currents at the battery pack over a plurality of times.
However, some cells among the plurality of cells constituting a battery pack reach an advanced state of depletion while the rest of the cells, which account for a majority, remain virtually intact in reality. In other words, there is often marked inconsistency in the depletion characteristics among the plurality of cells and, as a result, if the battery SOC (state of charge) is calculated by using the averaged deterioration factor as in the related art, an error is bound to manifest between the calculated battery SOC and the actual battery SOC.
An object of the present invention is to provide an apparatus for and method of detecting a battery pack abnormality enabling to detect a cell abnormality by accurately ascertaining the state of depletion of a battery pack through an arithmetic operation.
In the battery pack abnormality detection apparatus that detects an abnormality occurring in a battery pack achieved by connecting in series a plurality of modules each constituted of a plurality of cells comprising a plurality of cell controllers connected in series to individually control the modules and a battery controller that controls the plurality of cell controllers and detects a cell abnormality, a cell controller at an uppermost stage among the plurality of cell controllers detects the individual states of depletion of the plurality of cells in the corresponding module and outputs the state of depletion of the cell at the most advanced state of depletion among the detected states of depletion to the cell controller at the next stage, the plurality of cell controllers connected at the subsequent stages succeeding the cell controller at the uppermost stage each detect the individual states of depletion of the plurality of cells in the corresponding module, compare the state of depletion of the cell at the most advanced state of depletion among the detected states of depletion with the state of depletion input from the cell controller at the preceding stage and output the most advanced state of depletion to the cell controller at the next stage, and the battery controller detects a cell abnormality based upon the most advanced state of depletion input from the cell controller at the lowermost stage.
A battery pack abnormality detection method for detecting an abnormality occurring in a battery pack achieved by connecting in series a plurality of modules each constituted of a plurality of cells comprising detecting individual states of depletion of the plurality of cells in the uppermost module and outputting the state of depletion of the cell at the most advanced state of depletion among the detected states of depletion to the cell controller at the next stage by a cell controller at an uppermost stage among the plurality of cell controllers, detecting individual states of depletion of the plurality of cells in the subsequent module succeeding the uppermost module, comparing the state of depletion of the cell at the most advanced state of depletion among the detected states of depletion with the state of depletion input from the cell controller at the preceding stage and outputting the state of depletion in a more advanced state to the cell controller at the next stage by a plurality of cell controllers connected at subsequent stages succeeding the cell controller at the uppermost stage and detecting a cell abnormality based upon the state of depletion in the most advanced state input from the cell controller at the lowermost stage by the battery controller.